The fifth wave of the COVID-19 pandemic broke out in Hong Kong at the beginning of the year, which was gradually brought under control in April, and dropped below 1,000 new cases for the first time on April 15.
The HKSAR government has gradually relaxed social distancing measures since April 21. The daily new cases dropped further to 200 to 300 cases in mid-to-late May. However, the number climbed gradually and resurged to over 1,500 cases in the past week. Fortunately, up till now, the number of hospitalizations, severe illnesses and deaths remain low and stable.
Infection from the omicron variant started in South Africa in November 2021 and has gradually become the dominant strain worldwide. The number of daily new cases and related deaths peaked globally in January and has rapidly declined since then. Therefore, many countries have significantly relaxed their social-distancing and travel restrictions. However, the highly contagious omicron subvariants BA.4 and BA.5 are now fueling new COVID-19 cases globally. The World Health Organization announced that the BA.4 and BA.5 subvariants have been detected in over 40 countries; their infectivity is 20 to 30 percent higher than the BA.1 and BA.2 subvariants. These two new subvariants are now sweeping across Europe, leading to a significant rebound in many European countries and a surge in hospitalizations. In particular, the pandemic in Portugal is the most severe, where the BA.4 and BA.5 subvariants have become the most dominant strains, accounting for 50.6 percent of infections, and the number of hospitalizations was comparable to the peak level in January this year. An analysis from the Financial Times showed that hospitalizations were also rising in France, the UK and Germany. In the United States, the proportion of BA.4 and BA.5 infections increased by 21 times in just 35 days. Paul Bieniasz, a virologist at Rockefeller University, warned that millions of Americans could become reinfected in the future. A recent study concluded that BA.4 and BA.5 replicate more efficiently in human lung cells than their cousins do. As compared to BA.1 and BA.2, which mainly infect the upper respiratory tract, BA.4 and BA.5 could potentially more likely affect the lower respiratory tract, resulting in pneumonia.
The fifth wave reached its peak in early March with more than 70,000 new cases per day. Our bodies develop both cellular and humoral immunities after infection. Among them, antigen-specific antibodies from the humoral immunity will decline significantly over time. The protection against reinfection is strongest in the first three months after infection, and gradually decreases over the second three months, and most of its protection wears off six months after infection. The number of infections is anticipated to rise as we enter the fall in September. Moreover, protection from natural infection or vaccination may not be good enough to prevent infection from BA.4 and BA.5. Therefore, it is of critical importance to prevent BA.4 and BA.5 infection from spreading into the community.
At present, over 100 BA.4/BA.5 cases have been reported in Hong Kong. Fortunately, contact tracing has successfully identified the chains of transmission and so far, there is no spreading in the community. As Hong Kong may further relax its travel restrictions, we must be well prepared for a possible sixth wave in the autumn and winter coming from the BA.4/BA.5 subvariants. Citizens must keep vigilant, especially in the following four areas.
First, one should wear a high-efficiency mask to better protect oneself. A study by the American Conference of Governmental Industrial Hygienists reported that in a room with two individuals, both wearing surgical masks but one with an omicron infection and one without, it took only one hour for the healthy individual to get infected. Whereas if both individuals were wearing N95 masks, it took 25 hours for the healthy one to get infected. The authors have previously suggested that the authorities amend the Prevention and Control of Disease (Wearing of Masks) Regulation (Cap. 599I) (hereinafter referred to as “the Regulation”), and revise the definition of “mask” in the Regulation to “high-efficiency masks” (i.e., KN95, N95 or KF94 mask). The authors strongly urge all citizens to wear these high-efficacy masks to protect themselves and others before the proposed suggestion becomes implemented.
Second, it is desirable to make good use of rapid antigen testing (RAT) to identify people with a high viral level, thus a high infectivity. The requirement for a RAT negative result before going to school or high-risk places like bars should remain in force. Extension of such a requirement to other premises like cinemas, gymnasiums, and beauty parlors might need to be considered later.
Third, one should try avoiding crowded places, especially with space confinement like inside public transport and cinemas, etc. At the same time, reduce attending social activities that involve mask removal such as dining out or going to bars.
Fourth, both the government and the public should join hands to increase the vaccination rate. According to the SAR government, more than 70 percent of those who died during the fifth wave were unvaccinated. Research conducted by the University of Hong Kong showed that both vaccines (Sinovac and BioNTech) used in Hong Kong are effective in preventing omicron infection. The effectiveness of preventing severe illness and death after three injections of the vaccine is over 97 percent. Through the joint efforts of the government and people of Hong Kong, the overall vaccination rates of the first and second doses have reached 92.5 percent and 88.3 percent respectively. The uptake rate of the third dose has also exceeded 60 percent in Hong Kong. Facing the new variants of the coronavirus, the government must accelerate the promotion of the third or even the fourth dose, and pay close attention to the latest vaccine developments. Many pharmaceutical companies around the world are also accelerating their vaccine development against the new omicron variants.
The government must also monitor the number of imported BA.4/BA.5 cases. If these cases are not caught during the quarantine period, they could be the seeds for community outbreaks. The policies on the duration of quarantine and flight suspension must be continuously monitored and adjusted accordingly, in order to strike a good balance between the risk of community transmission and the impact on the economy.
The authors believe that through joint efforts of the government and the public, Hong Kong can prevent or mitigate the sixth wave if we remain vigilant and with good forward planning and appropriate actions.
Dennis Lam is a Legislative Council member and Hong Kong deputy to the National People's Congress. Kelvin Wan is managing editor, COVID-19 FAQs, Asia-Pacific Journal of Ophthalmology.
The views do not necessarily reflect those of China Daily.